Stop motion mechanism for sewing machines



June 30, 1942. j HQZA 2,288,135

STOP MOTION MECHANISM FOR SEWING MACHINES 48 Filed March 29, 1940 8 Patented June 30, 1942 s'ror MOTION MECHANISM FOR'SEWING MACHINES John Hoza, Belcamp, Md.

Application March 29, 1940, Serial No. 326,818 In Czechoslovakia May 28, 1938 Claims.

This invention relates to a stop-motion mechanism for sewing machines which renders possible instantaneous arrest of the needle in its uppermost or its lowermost position at choice.

In constructions heretofore usual, when the machine is brought to rest, the needle may be in any one of an unlimited number of positions irrespective of the nature of the work; moreover the arrest of the needle may take a relatively long time.

For many operations, as for example, normal sewing, it is desirable that the needle be arrested in its uppermost position, so that the sewn article may be readily removed from the machine and replaced by another article. For other classes of work, for example, for sewing ornamental seams in different directions, it is desirable that the needle and its thread remain in the lowermost position, so that the work may be rotated round the needle and otherwise orientated, without necessity for forming a useless stitch on the upper side of the work. It is also desirable for the arrest of the needle to take place practically instantaneously.

The stop-motion mechanism according to the invention renders it possible to effect, in a simple manner, instantaneous arrest of the needle in its uppermost or lowermost position.

According to the invention, there is employed for driving a needle bar actuating shaft a combined clutch and brake, the clutch depending for its operation on the combined action of friction and centrifugal force, the centrifugal force being exercised on a locking device for stopping the needle in its uppermost or in its lowermost position.

The embodiment of the invention is illustrated in the accompanying drawing in which Fig. 1 is an end view, and Fig. 2 an axial section showing clearly the clutch and brake mechanism. Fig. 3 is an end view of the brake disc with locking device, partly in section.

I denotes the main shaft of the sewing machine on which is mounted the axially shiftable belt pulley 2 freely rotatable on a ball bearing. Adjacent to said pulley on the shaft I is the endwise movable flywheel 3 adapted to be actuated by the rock lever 4 operatively connected with said flywheel by means of the pin 5 penetrating a bore of the shaft I and the transverse pin 6, said lever 4 being operable by actuation of a treadle lever, not shown, by way of the chain 22. The flywheel 3 is unitary with a brake disc 3 and is movable axially on the shaft I to which it is fitted by a spline I. Fitted to the brake disc 55 power.

3 in a recess formed therein is a radially movable counterweight 8, urged by a spring 9, the inner end of which weight carries the U-shaped locking member I0. The opposite end of the member I0 engages the spring-urged pin II connected with the lever I2 and with the pin I3 abutting on the bush I4 on which the belt pulley 2 is rotatably mounted. Between the flywheel 3 and the machine frame is interposed the brake disc I6 adjoined to the bushing 23 surrounding the shaft. The brake disc I6 presents a groove I1 engageable by the pin II when the latter is shifted. The groove I I is interrupted by the straight diametral groove I8 in which are movable two slides I9 and 20. Each of these slides has a brake stop I5 or I5 which renders possible the locking of the shaft with the needle in its uppermost or in its lowermost position. For the purpose of unitary actuation the slides I9 and 20 are connected by means of the yoke 2I represented in chain lines in Fig. 1 and may be operated by means of a knee lever.

A sewing machine having a speed of about 3,000 revolutions per minute naturally cannot be abruptly stopped but it may be instantly brought to rest without risk of injury when the shaft is rotating at about 500 revolutions per minute. Normally, the dropping of the-speed from 5,000 to 500 revolutions per minute occupies a fairly long time, which is eliminated by the construction according to the invention. This result is rendered possible by reason that, with the machine running at a high number of revolutions, first the flywheel 3 is braked by engagement with the brake disc I6, it being understood that during this braking operation the weight 8 moves inward radially, and, as soon as the centrifugal force has so far diminished that the weight is overcome by the spring 9, the member I0 releases the pin II which enters the groove ll of the brake disc and thereby efl'ects the instantaneous stoppage of the machine, according to the position of the slides I9, 20, either in the uppermost or in the lowermost position of the needle.

The starting of the sewing machine, that is, the throwing in of the friction clutch for the purpose of power transmission is effected as follows:

By depression of the treadle connected by a chain 22 or the like with the lever I, said lever, which is connected by means of the stud 5 and the pin 6 with the flywheel 3, presses the flywheel against the belt pulley 2 which rotate continuously, being driven directly from the source of With the shift of the flywheel towards the belt pulley 2 the pin I 3 abuts against the bushing H and rocks the lever I2 which releases the pin II from engagement with the stop I! or I! and releases the flywheel. With increased or reduced pull on the chain 22 there is effected more rapid or slower running of the machine.

If now the machine is to be brought to rest, the treadle lever and the chain 22 or the like connected therewith are released. On this release the flywheel 3 is pressed by means of the lever 4 against the brake disc l8 and the machine is braked. The braking is the result of two operations. First, with the pressure of the flywheel 3 against the brake disc I 6 the number of revolutions of the flywheel 3 is reduced. Thereby the centrifugal force of the counter-weight 8 is so diminished that the spring 9 overcomes the centrifugal force. Consequently the weight 8 moves towards the centre of the shaft, the member Ill connected with the weight clearing the path of the pin H and the latter engaging the groove Il under the pressure of the spring, moving in the groove until it engages the adjusted stop l or l5 whereby the needle is brought to rest either in its lowermost or in its uppermost position, depending on which stop I5 or I5 is within the annular groove I! in which the pin ll moves.

It will be seen that, as soon as the machine falls to such a speed that the centrifugal force of the weight 8 is overcome by the power of the spring 9, after release of the treadle lever holding the flywheel 3 in engagement with the belt pulley 2, the machine will instantaneously be brought to rest.

The stress of the spring 9 may be adjusted to ensure arrest of the machine when the shaft l is rotating at a predetermined number of revolutions per minute.

The invention is not restricted to the particular construction illustrated, and details may be varied without departure from the essence of the invention.

I claim:

1. In a stopping mechanism for sewing machines, a driven shaft, a continuously rotating drive pulley rotatably mounted on said driven shaft, and manually controllable means for connecting said driven shaft operatively with said pulley and adapted to cause said driven shaft to be stopped in at least one predetermined position, a stationary brake disc provided with at least one stop member, said manually controllable means including a unitary flywheel and brake member slidably mounted on said driven shaft and rotating therewith, a manually operable lever for moving said flywheel and brake member into frictional engagement with said drive pulley, thereby causing a rotation of said driven shaft, spring means for moving said flywheel and brake member into engagement with said stationary brake disc when said manually operable lever is released, a counterweight slidably mounted on said flywheel, and a locking pin slidably mounted on said flywheel, said locking pin being controlled by said counterweight to move at a predetermined low speed of the flywheel into a position in which one end of said pin engages said stop member on said stationary brake disc when said manually operable lever is released, thus stopping the driven shaft in the desired predetermined position.

2. In a stopping mechanism for sewing machines, a driven shaft, a continuously rotating drive pulley rotatably mounted on said driven shaft. and manually controllable 'means for con-'"" necting said driven shaft operatively with said pulley and adapted to cause said driven shaft to be stopped selectively in two different predetermined positions, a stationary brake disc provided with two simultaneously adjustable stop members, said manually controllable means including a unitary flywheel and brake member slidably mounted on said driven shaft and rotating therewith, a manually operable lever for moving said flywheel and brake member into frictional engagement with said drive pulley, thereby causing a rotation of said driven shaft, spring means for moving said flywheel and brake member into engagement with said stationary brake disc when said manually operable lever is released, a counterweight slidably mounted on said flywheel, and a locking pin slidably mounted on said flywheel, said locking pin being controlled by said counterweight to move at a predetermined low speed of the flywheel into a position in which one end of said pin engages one of said stop members on said stationary brake disc when said manually operable lever is released, thus stopping the driven shaft in the desired predetermined position.

8. In a stopping mechanism for sewing machines, a driven shaft, a continuously rotating drive pulley rotatably mounted on said driven shaft, and manually controllable means for connecting said driven shaft operatively with said pulley and adapted to cause said driven shaft to be stopped in at least one predetermined position, a stationary brake disc provided with at least one stop member, said manually controllable means including a unitary flywheel and brake member slidably mounted on said driven shaft and rotating therewith, a manually operable lever for moving said flywheel and brake member into frictional engagement with said drive pulley, thereby causing a rotation of said driven shaft, spring means for moving said flywheel and brake member into engagement with said stationary brake disc when said manually operable lever is released, a counterweight slidably mounted on said flywheel, a locking pin slidably mounted on said flywheel, said locking pin being controlled by said counterweight to move at a predetermined low speed of the flywheel into its operative position in which one end of said pin engages said stop member on said stationary brake disc when said manually operable lever is released, thus stopping the driven shaft in the desired predetermined position, and means including a pivoted lever mounted on said flywheel for returning said locking pin into its inoperative position when said manually operable lever is actuated to move said unitary flywheel and brake member in engagement with said drive pulley.

4. In a stopping mechanism for sewing machines, a driven shaft, a continuously rotating drive pulley rotatably mounted on said driven shaft, and manually controllable means for connecting said driven shaft operatively with said pulley and adapted to cause said driven shaft to be stopped selectively in two different predetermined positions, a stationary brake disc provided with two simultaneously adjustable stop members, manually operable means for adjusting said stop members so that either one of them is in a position to stop the driven shaft, said manually controllable means including a unitary flywheel and brake member slidably mounted on said driven shaft and rotating therewith, a manually operable lever for moving said flywheel and brake member into frictional engagement with said drive pulley, thereby-causing a rotation of said driven shaft, spring means for moving said flywheel and brake member into engagement with said stationary brake disc when said manually operable lever is released, a counterweight slidably mounted on said flywheel, a locking pin slidably mounted on said flywheel, said locking pin being controlled by said counterweight to move at a predetermined low speed of the flywheel into its operative position in which one end of said pin engages one of said stop members on said stationary brake disc when said manually operable lever is released, thus stopping the driven shaft in the desired predetermined position, and means on said flywheel for automatically returning said locking pin into its inoperative position when said flywheel and brake member is moved into frictional contact with said drive pulley.

5. Stop-motion mechanism for sewing machines for stopping the machine with the needle in a predetermined position, comprising, in combination with the main shaft, a unitary flywheel and brake disc slidable on said shaft, a second stationary brake disc cooperating with said first named brake disc, a stop mounted manually adjustably on said stationary brake disc, a counterweight carried slidably by said flywheel and subject to the action of centrifugal force, and a locking device on said flywheel including a slidably mounted spring actuated pin which upon movement of said counterweight in response to a predetermined reduction of speed of said flywheel is released to engage said stop.

JOHN HOZA. 

